"Cane toads moving across Australia are the fastest amphibians on Earth after their rapid evolution from slow-moving homebodies into road warriors over the past 70 years," Rick Shine at Sydney University said.

"We are seeing toads in the Northern Territory with spinal arthritis – big, bony lumps on their spine," said Mr Shine.

Cane toads are one of Australia's worst environmental mistakes, ranking alongside the catastrophic introduction of rabbits.

The toads, introduced in a batch of 101 from Hawaii in 1935 in a failed bid to control native cane beetles, have spread 3,000km (1,900 miles) from northeast Queensland to Darwin in Australia's tropical north.

The spread of the toads, whose skin is poisonous, has led to dramatic declines in populations of native snakes, goanna lizards and quolls, a cat-sized marsupial.